This invention relates to an apparatus for automatically analyzing and data processing combustible gases dissolved in the insulating oil of oil-immersed equipment, for example, oil-immersed transformers. More particularly, it relates to an apparatus for automatically analyzing gases in oil which is provided with a function for determining whether there is an abnormality in oil-immersed equipment based on the increasing trend or decreasing trend of the analyzed results of the quantities of combustible gases and a function for automatically changing the sampling period of oil sampling and analytical processing routines.
When an abnormality such as arc discharge, corona discharge or local heating has taken place in an oil-immersed equipment, an electrical insulating material, for example, insulating oil or insulating paper near an abnormal part is decomposed to produce combustible gases. The majority of the produced combustible gases are dissolved in the insulating oil. Therefore, the combustible gases in the oil have hitherto been analyzed in order to find out the abnormality in the oil-immersed equipment at an early stage and to prevent any accident from occurring. As apparatuses for detecting the combustible gases in the oil, the mainstream has heretofore been formed by off-line processing routine wherein a man samples the oil from the oil-immersed equipment and then analyzes the sampled oil with an analyzer such a gas chromatograph. In recent years, an automatic analyzing apparatus of on-line processing routine, which is connected to a transformer by a pipe or two pipes and which automatically performs steps from oil sampling to analysis, has also become commercially available.
The analyzing apparatus of both types can detect the absolute values of the quantities of the combustible gases in the oil. However, neither of them can execute the determination processing of an increasing trend or decreasing trend of the analyzed results of the combustible gas quantities in the oil, the determination processing of the trend being another important factor, for detecting early the abnormality in oil-immersed equipment, and a man has always observed the trend and determined the presence or absence of the abnormality. As illustrated in FIG. 1, with the method of foreknowing the abnormality on the basis of only the absolute values of the combustible gas quantities in the oil, the abnormality is found out at a point of time t.sub.2. In contrast, the method of foreknowing the abnormality in the oil-immersed equipment on the basis of the increasing trend of the analyzed results makes it possible to find out the abnormality at a point of time t.sub.1 before the point of time t.sub.2. Therefore, the latter method is an effective measure with which the abnormality can be found out earlier than with the former method. The prior art, however, has had the disadvantages that labor for collecting and processing data is required and that skills are required for detecting the trends and for determining the presence or absence of the abnormality. Another disadvantage is that, if the result of determination by a man as stated above is "requiring attention", much labor is expended in shortening the sampling period of oil sampling and analytical processing routines in order to render a more precise determination.